A contemporary wireless communication system, such as distributed antenna system 10, is shown in FIG. 1, and includes a number of remote units 12 distributed to provide coverage within a service area of the system 10. In particular, each remote antenna unit 12 typically includes an antenna 14 and suitable electronics. Each remote unit is coupled to a master unit 16. Each master unit 16 is, in turn, coupled to a RF combination network 18 that combines the signals from at least one single-input- and single-output (“SISO”) base transceiver station (“BTS,” or more simply, “base station”) 20 (hereinafter, “SISO BTS” 20). The system 10 may further include a system controller 22 to control the operation of each master unit 16. As illustrated in FIG. 1, the system 10 may include a plurality of master units 16 and a plurality of SISO BTSs 20, each master unit 16 configured to provide a combination of the signals from at least two SISO BTSs 20 to its respective remote units 12.
As illustrated in FIG. 1, each remote unit 12 may broadcast a wireless signal 24 that, in turn, may be received by a wireless device 26 that may be a mobile device, such as a telephone device or a computing device. In particular, and as discussed above, the wireless signal 24 from each remote unit 12 may be a combination of signals from the at least two SISO BTSs 20. Thus, the wireless device 26 may communicate with the system 10 through any of the wireless signals 24 from the remote units 12.
To improve wireless communications, such as communications from a base station to mobile devices, Multiple-Input/Multiple-Output (“MIMO”) technology might be utilized to provide advanced solutions for performance enhancement and broadband wireless communication systems. Through various information series studies, it has been shown that substantial improvements may be realized utilizing a MIMO technique with respect to the traditional SISO systems. MIMO systems have capabilities that allow them to fully exploit the multi-path richness of a wireless channel. This is in contrast with traditional techniques that try to counteract multi-path effects rather than embrace them. MIMO systems generally rely upon multi-element antennas at both of the ends of the communication links, such as in the base station and also in the mobile device. In addition to desirable beam-forming and diversity characteristics, MIMO systems also may provide multiplexing gain, which allows multi data streams to be transmitted over spatially-independent parallel sub-channels. This may lead to a significant increase in the system capacity. Generally, the systems illustrated in FIG. 1 cannot take advantage of MIMO technology.
For example, the wireless device 26 of FIG. 1 communicates with only one of the remote units 12, though it may be in the range of a plurality of remote units 12. The wireless signals 24 from each remote unit are typically at the same frequency and carry the same data, and communication between a plurality of remote units 12 and the wireless device 26 simultaneously may result in signal degradation and collisions. Moreover, data bandwidth from the wireless device 26 is constricted to the speed of reception and processing of data from one remote unit 12.
It is therefore, desirable to take advantage of MIMO signals within a wireless system, such as distributed antenna system, without requiring an entirely new system to be installed for handling MIMO signals.